1. Field of the Invention
The present invention relates to electrical connectors, and more particularly, to a land grid array (LGA) socket having accessorial pressing members for reliable electrical connection between an LGA package and a circuit substrate, such as a printed circuit board (PCB).
2. Description of the Prior Art
An integrated circuit (IC) package having conductive pads arranged on a bottom surface thereof in a land grid array (LGA) fashion is known as an LGA package. LGA packages are widely used due to relatively low height and reliable electrical characteristics.
Connectors for removably mounting an LGA package on a PCB are known as LGA sockets. Normally, an LGA socket comprises a socket body and a stiffener attached to the socket body. The socket body defines an array of passageways for receiving contacts therein. Each contact has a spring arm and a terminal section protruding from opposite external surfaces of the socket body. The spring arm is resiliently urged to electrically engage with a corresponding conductive pad on the LGA package, while the terminal section is electrically mounted to the PCB.
When the LGA package is positioned on the socket body, the conductive pads of the LGA package rest on corresponding contacts received in the socket body. Electrical connection between the conductive pads and the corresponding contacts is obtained via elastic deflection and deformation of the spring arms. Thereupon, it is necessary to exert sufficient engaging force against the LGA package to maintain electrical engagement between the conductive pads and the corresponding contacts.
Heretofore, various LGA sockets each including a socket plate and a load lever to provide the engaging force are disclosed. Referring to FIGS. 5 to 7, a conventional LGA socket 8 comprises a socket body 82 receiving a plurality of contacts 81, a stiffener 83 attached to the socket body 82, and a socket plate 84 and a load lever 85. The socket plate 84 and the load lever 85 are pivotally assembled to opposite ends of the stiffener 83 respectively to fasten the LGA package 100 jointly.
The socket plate 84 includes a connecting side 840 to assemble to the stiffener 83, a pressing side 841 to engage with the load lever 85, and a pair of lateral sides 842 respectively and integrally connected to two ends of the connecting side 840 and the pressing side 841. The lateral sides 842 of the socket plate 84 are bent slightly downward to form a pair of clasping sections 843 thereunder.
In assembly, prior to positioning the LGA package 100 on the socket 8, the socket plate 84 and the load lever 85 are rotated away from the socket body 82. After the LGA package 100 is set on the socket body 82, with the conductive pads (not shown) resting on the corresponding contacts 81, the socket plate 84 is rotated with respect to the socket body 82 till the clasping sections 843 meet a top surface of the LGA package 100. Whereafter, the load lever 85 is rotated to clip the socket plate 83 and push the LGA package 100 to move downward. In a closed position, the clasping sections 843 press on the top surface of the LGA package 100 and hold the LGA package 100 in position, thereby providing the engaging force to assure electrical connection between the conductive pads and the corresponding contacts 81.
When the socket plate 84 is rotated to fasten the LGA package 100, the part of the socket plate 84 adjacent the connecting side 840 contacts the LGA package 100 foremost, which is liable to cause the LGA package 100 become inclined relative to and slide along a top surface of the socket body 82. As a result, the LGA package 100 may engage with the sidewalls of the socket body 82. When the LGA package 100 is driven down to electrically mate with the contacts 81, a considerable friction force between the LGA package 100 and the sidewalls is generated. The friction force will provide a vertical force and moment to tilt the LGA package and prevent the LGA package 100 from moving downward. Therefore, the conductive pads, especially the conductive pads distant from the connecting side 840, are prone to separate from the corresponding contacts received in the socket body 82. This will surely disturb electrical engagement between the conductive pads of the LGA package and the corresponding contacts 81 received in the socket body 82.
Heretofore, various efforts have been provided to eliminate the friction force between the LGA package and the sidewalls of the socket body, such as enhancing the loading force. This will increase interactional force among each electrical component and is prone to unfavorably affect electrical characteristics of the LGA socket.
Hence, a new LGA socket which overcomes the above-mentioned disadvantages of the prior art is desired.